21, Number 3, September 2010
Tina L. Huang
Omega-3 Fatty Acids, Cognitive Decline, and Alzheimer’s Disease: A Critical Review and Evaluation of the Literature
Abstract: The precipitous decline of memory and independence associated with cognitive decline, dementia, and Alzheimer’s disease is emotionally and financially devastating to patients, their families, and caretakers. Studies from animal models and cell cultures have shown that omega-3 fatty acids (n-3 FAs) are neuroprotective during development and aging. Numerous epidemiologic, postmortem, and clinical trials have been published on fish or n-3 FAs and Alzheimer’s disease, dementia, or cognitive decline. Yet results across the literature in humans are inconsistent and thus difficult to interpret. This review provides background and context needed for interpretation of the findings, summaries of the literature grouped by longitudinal studies of fish, dietary n-3 FAs, blood levels of fatty acids, postmortem studies, and clinical trials, and subsequent interpretation of findings. Possible reasons for discrepancies in the literature are presented throughout, and conclusions suggest directions for future research.
Francesco Panza, Vincenza Frisardi, Cristiano Capurso, Bruno P. Imbimbo, Gianluigi Vendemiale, Andrea Santamato, Grazia D’Onofrio, Davide Seripa, Daniele Sancarlo, Alberto Pilotto, Vincenzo Solfrizzi
Metabolic Syndrome and Cognitive Impairment: Current Epidemiology and Possible Underlying Mechanisms
Abstract: A possible role of vascular and lifestyle-related factors was recently proposed for age-related changes of cognitive function, predementia syndromes, and cognitive decline of degenerative (Alzheimer’s disease, AD) or vascular origin (vascular dementia, VaD). At present, cumulative evidence suggests that vascular risk factors may be important in the development of mild cognitive impairment (MCI), dementia, and AD. Among vascular-related factors, metabolic syndrome (MetS) has been associated with the risk of cognitive decline, overall dementia, and VaD, but contrasting findings also existed on the possible role of MetS in AD. If MetS is associated with increased risk of developing cognitive impairment, regardless of mechanism, then early identification and treatment of these individuals at risk might offer new avenues for disease-course modification. Strategies towards early and effective risk factor management could be of value in reducing risk of metabolic and cognitive decline. Future research is needed to confirm the association between MetS and cognitive impairment and to determine the exact mechanism linking them. Such would provide important insights into the causes and interdependencies of predementia and dementia syndromes, and inspire novel strategies for treating and preventing these disorders. At present, vascular risk factor and MetS management could be employed to delay the onset of dementia syndromes or to prevent the progression of predementia syndromes. In the future, trials could be undertaken to determine whether modifications of these risk factors, including inflammation, could lower risk of developing cognitive decline.
William R. Brown (Handling Associate Editor: Jack de la Torre)
A Review of String Vessels or Collapsed, Empty Basement Membrane Tubes
Abstract: String vessels are thin connective tissue strands, remnants of capillaries, with no endothelial cells; they do not carry blood flow. They occur in numerous species, particularly in the central nervous system, but can occur in any tissue where capillaries have died. String vessels are often associated with pathologies such as Alzheimer’s disease, ischemia, and irradiation, but are also found in normal human brains from preterm babies to the aged. They provide a record of the original blood vessel location, but gradually disappear after months or years. There have been numerous studies of string vessels (acellular capillaries) in the retina, because retinal vessels can be seen in great detail in whole mounts after trypsin digestion. Capillary regression occurs by apoptosis, synchronously along capillary segments, with macrophages engulfing apoptotic endothelial cells. Macrophages may cause the apoptosis, or the regression may be triggered by loss of the endothelial cell survival factor VEGF. VEGF expression is induced by hypoxia and promotes capillary growth. Cessation of blood flow eliminates the shear stress that helps maintain endothelial cell survival. Capillaries can re-grow by proliferation and migration of endothelial cells into empty basement membrane tubes, which provide a structural scaffold, replete with signaling molecules. This is a problem in tumor control, but useful for recovery from capillary loss. There is an age-related waning of VEGF expression in response to hypoxia. This causes an age-related decline in cerebral angiogenesis and results in neuronal loss. It may also contribute to the proposed age-related loss of brain reserve.
Manjeet Singh, Dang Than Nam, Madeleine Arseneault and Charles Ramassamy
Role of By-Products of Lipid Oxidation in Alzheimer’s Disease Brain: A Focus on Acrolein
Abstract: Abundant data consistently support the idea that oxidative stress occurs and is a constant feature of Alzheimer’s disease (AD). Some recent evidence indicated that this phenomenon is an early event and might be implicated in the pathogenesis of this disease. Lipid peroxidation leads to the formation of a number of aldehydes by-products, including malondialdehyde (MDA), 4-hydroxy-2-nonenal (HNE), and acrolein. The most abundant aldehydes are HNE and MDA while acrolein is the most reactive. Increased levels of specific HNE-histidine and glutathione-HNE Michael adducts in AD brain has been reported. Proteomic analysis demonstrated a large number of protein-bound HNE in AD brain. F2-isoprostanes (F2-IsoPs) levels and neuroprostanes were also significantly increased in mild cognitive impairment (MCI) patients and in late-stage AD. In brain from patients with AD, acrolein has been found to be elevated in hippocampus and temporal cortex where oxidative stress is high. Due to its high reactivity, acrolein is not only a marker of lipid peroxidation but also an initiator of oxidative stress by adducting cellular nucleophilic groups found on proteins, lipids, and nucleic acids. Interestingly, several data indicated that lipid peroxidation occurs in the brain of MCI and also in preclinical AD patients suggesting that oxidative damage may play an early role in the pathogenesis of AD. In this review, we will summarize some mechanisms implicated in the toxicity of by-products of lipid peroxidation such as IsoPs, HNE, and acrolein and their implication in AD.
Mariana Sinning, Jan Piere van Rooyen, Pablo Venegas-Francke, Carolina Vásquez, María Isabel Behrens, Alfredo Ramírez (Handling Associate Editor: Julie Schneider)
Clinical and Genetic Analysis of a Chilean Family with Early-Onset Autosomal Dominant Alzheimer’s Disease
Abstract: Autosomal dominant early-onset Alzheimer’s disease (ADEOAD) is associated predominantly with mutations in the genes that codify for presenilin 1 (PSEN1). Only a few ADEOAD families have been reported from Latin America. This is an extended Chilean pedigree affected by ADEOAD along 4 generations. The age of onset of dementia was between 38 and 42 years. Early manifestations were anxiety and depression. Mutation analysis revealed a heterozygous G to C transversion at position 438 of the mRNA in PSEN1 in all affected members. This is the first report of a Chilean family with ADEOAD to include mutation analysis.
Timo Sarajärvi, Seppo Helisalmi, Leila Antikainen, Petra Mäkinen, Anne Maria Koivisto, Sanna-Kaisa Herukka, Annakaisa Haapasalo, Hilkka Soininen and Mikko Hiltunen (Handling Associate Editor: Israel Ampuero)
Association Study of 21 Potential Alzheimer’s Disease Risk Genes Among Finnish Population
Abstract: Alzheimer's disease (AD) is a genetically complex disorder encompassing several individual susceptibility genes with low risk effects. To assess the risk gene effects in a cohort consisting of ~1300 Finnish AD patients and controls, 21 candidate gene polymorphisms were selected for genotyping on the basis of the meta-analyses retrieved from the AlzGene database. A significant genotype and allele association with AD was observed with rs1800629 in the tumor necrosis factor α (TNF). Risk analysis revealed a protective effect for the minor allele carriers of rs1800629. This suggests that genetic alteration in TNF gene may play a role in AD.
Esther S. Oh, Michelle M. Mielke, Paul B. Rosenberg, Alka Jain, Neal S. Fedarko, Constantine G. Lyketsos, Pankaj D. Mehta (Handling Associate Editor: Ralph Martins)
Comparison of Conventional ELISA with Electrochemiluminescence Technology for Detection of Amyloid-β in Plasma
Abstract: Plasma amyloid-β (Aβ) level could be useful as a non-invasive biomarker in Alzheimer’s disease research. We compared a multiplex electrochemiluminescence detection method with a well established ELISA method for plasma Aβ quantification. Compared to the ELISA method, electrochemiluminescence detection method demonstrates a statistically significant, but modest correlation. The reasons for this may include the differences in the affinities of antibodies, and purity and source of Aβ peptides used as standards. However, the advantages of electrochemiluminescence detection technology include short processing time and small sample volume. This comparison demonstrates the need for a further study in optimizing this system.
Beena Koshy*, Akinori Miyashita*, Pamela St. Jean*, Heide Stirnadel, Toshihiko Kaise, Justin P. Rubio, Vincent Mooser, Ryozo Kuwano, Michael C. Irizarry (Handling Associate Editor: Estrella Gómez-Tortosa) *Equal contribution
Genetic Deficiency of Plasma Lipoprotein-Associated Phospholipase A2 (PLA2G7 V297F Null Mutation) and Risk of Alzheimer’s Disease in Japan
Abstract: High plasma lipoprotein phospholipase A2 activity (Lp-PLA2) was reported to be a risk factor for dementia. A loss of function polymorphism in the Lp-PLA2 gene—PLA2G7 V279F—is found almost exclusively in Asians. In 1,952 subjects with late-onset AD and 2,079 non-demented controls recruited from Japan, the PLA2G7 null allele was not associated with risk or age at onset of AD: logistic regression OR 0.98 (95% CI 0.86-1.12, p=0.81) per additional null allele, adjusted for age/age at onset, gender, and APOE ε4. Genetic deficiency of Lp-PLA2 activity is not associated with a reduced risk of AD in the Japanese population.
Omar Nelson, Charlene Supnet, Huarui Liu, Ilya Bezprozvanny (Handling Associate Editor: Jonathan Geiger)
Familial Alzheimer’s Disease Mutations in Presenilins: Effects on Endoplasmic Reticulum Calcium Homeostasis and Correlation with Clinical Phenotypes
Abstract: Mutations in presenilins 1 and 2 (PS1 and PS2) are responsible for approximately 40% of all early onset familial Alzheimer’s disease (FAD) monogenic cases. Presenilins (PSs) function as the catalytic subunit of gamma-secretase and support cleavage of the amyloid-β protein precursor (AβPP). We previously discovered that PSs also function as passive endoplasmic reticulum (ER) calcium (Ca2+) leak channels and that most FAD mutations in PSs affected their ER Ca2+ leak function. To further validate the relevance of our findings to human disease, we here performed Ca2+ imaging experiments with lymphoblasts established from FAD patients. We discovered that most FAD mutations in PSs disrupted ER Ca2+ leak function and resulted in increased ER Ca2+ pool in human lymphoblasts. However, we found that a subset of PS1 FAD mutants supported ER Ca2+ leak activity, as ER Ca2+ pool was unaffected in lymphoblasts. Most of the “functional” mutations for ER Ca2+ leak were clustered in the exon 8-9 area of PSEN1 gene and segregated with the cotton wool plaques and spastic paraparesis clinical phenotype occasionally observed in PS1 FAD patients. Our findings with the “functional” and “non-functional” PS1 FAD mutants were confirmed in Ca2+ rescue experiments with PS double-knockout mouse embryonic fibroblasts. Based on the combined effects of the PS1 FAD mutations on ER Ca2+ leak and g-secretase activities we propose a model that explains the heterogeneity observed in FAD. The proposed model has implications for understanding the pathogenesis of both familial and sporadic AD.
Dustin T. Proctor, Elizabeth J. Coulson, Peter R. Dodd ( Handling Associate Editor: Raymond Chuen-Chung Chang)
Reduction in Post-Synaptic Scaffolding PSD-95 and SAP-102 Protein Levels in the Alzheimer Inferior Temporal Cortex is Correlated with Disease Pathology
Abstract: N-methyl-D-aspartate (NMDA) receptor-evoked excitotoxicity contributes to region-specific loss of glutamatergic synapses responsible for cognitive decline in Alzheimer’s disease (AD). Here, the post-synaptic scaffold proteins PSD-95 and SAP-102, which regulate NMDA receptor synaptic activity and expression, were investigated in human AD autopsy brain tissue. Using absolute quantification real-time PCR, we detected reduced expression of synaptophysin in both the pathologically susceptible inferior temporal cortex and hippocampus, consistent with previous reports. PSD-95 and SAP-102 mRNA was reduced, albeit not significantly. Proteins were precisely quantified against recombinant truncated protein standards. No differences were observed for proteins in AD spared occipital cortex between AD cases and controls. PSD-95 and SAP-102 protein expression was markedly reduced in the AD inferior temporal cortex. Both mRNA and protein levels were reduced according to disease severity. SAP102 protein levels were significantly reduced in AD subjects carrying a copy of the APOEε4 allele. This is the first study to investigate SAP-102 in the aging human brain and suggest a possible mechanism for NMDA receptor expression aberrations in AD.
Xiaojuan Wang, Anfeng Xing, Changlei Xu, Qing Cai, Hong Liu, Liang Li (Handling Associate Editor: Chengxin Gong)
Cerebrovascular Hypoperfusion Induces Spatial Memory Impairment, Synaptic Changes, and Amyloid-β Oligomerization in Rats
Abstract: Cerebrovascular hypoperfusion occurs prior to the clinical symptoms of Alzheimer’s disease (AD) and represents the most accurate indicator predicting whether an individual develops AD at a future time. To study how cerebrovascular hypoperfusion contributes to AD, we induced cerebrovascular hypoperfusion by bilateral carotid occlusion surgery in adult rats and investigated its impacts on spatial memory, synapses, and accumulation of oligomeric amyloid-β. We found progressive spatial memory deficits, as tested by Morris water maze, starting 30 days after occlusion surgery. The memory deficits were accompanied with decrease in synaptic density and alterations of synaptic ultrastructure in the CA1 area of the hippocampus, as evaluated by electron microscopy. By using immunoelectron microscopy, we also found time-dependent accumulation of oligomeric amyloid-β in the hippocampus, especially in the axonal terminals after chronic cerebrovascular hypoperfusion. Western blot analysis revealed decreased levels of postsynaptic density-95 (PSD-95) and synaptophysin in rat brains after chronic cerebrovascular hypoperfusion. Our findings provide novel insight into the mechanism by which chronic cerebrovascular hypoperfusion contributes to the pathogenesis of AD.
Yan Zeng, Danyun Zhao and Cui-Wei Xie
Neurotrophins Enhance CaMKII Activity and Rescue Amyloid-β-Induced Deficits in Hippocampal Synaptic Plasticity
Abstract: Amyloid-β (Aβ) peptide-induced impairment of hippocampal synaptic plasticity is considered an underlying mechanism for memory loss in the early stages of Alzheimer’s disease and its animal models. We previously reported inhibition of long-term potentiation (LTP) and miniature excitatory postsynaptic currents by oligomeric Aβ1-42 at hippocampal synapses. While multiple cellular mechanisms could be involved in Aβ-induced synaptic dysfunction, blockade of activity-dependent autophosphorylation of Ca2+ and calmodulin-dependent protein kinase II (CaMKII) appeared to be a major component of Aβ action in our studies. The present study further tested this hypothesis and examined the therapeutic potential of trkB receptor-acting neurotrophins in rescuing Aβ-induced synaptic and signaling impairments. As expected, treatment of rat hippocampal slices with Aβ1-42 significantly reduced LTP in the Schaffer collateral-CA1 pathway and dentate medial perforant path. LTP-associated CaMKII activation and AMPA receptor phosphorylation were blocked by Aβ1-42 at the same concentration that inhibited LTP. Aβ-induced LTP impairment, however, was prevented when slices were co-treated with neurotrophin 4 (NT4). Western blotting and immunohistochemical analyses confirmed that treatment with NT4 or brain-derived neurotrophic factor, another trkB-acting neurotrophin, could oppose Aβ action, enhancing autophosphorylation of CaMKII, and AMPA receptor phosphorylation at a CaMKII-dependent site. These findings support the view that CaMKII is a key synaptic target of Aβ toxicity as well as a potential therapeutic site of neurotrophins for Alzheimer’s disease.
John S.K. Kauwe*, Carlos Cruchaga*, Sarah Bertelsen, Kevin Mayo, Wayne Latu, Petra Nowotny, Anthony L. Hinrichs, Anne M. Fagan, David M. Holtzman, Alzheimer’s Disease Neuroimaging Initiative, Alison M. Goate (Handling Associate Editor: Daniela Galimberti) *Co-first authors with equal contributions
Validating Predicted Biological Effects of Alzheimer’s Disease Associated SNPs Using CSF Biomarker Levels
Abstract: Recent large-scale genetic studies of late-onset Alzheimer’s disease have identified risk variants in CALHM1, GAB2, and SORL1. The mechanisms by which these genes might modulate risk are not definitively known. CALHM1 and SORL1 may alter amyloid-β (Aβ) levels and GAB2 may influence phosphorylation of the tau protein. In this study we have analyzed disease associated genetic variants in each of these genes for association with cerebrospinal fluid (CSF) Aβ or tau levels in 602 samples from two independent CSF series. We failed to detect association between CSF Aβ42 levels and small nucleotide polymorphisms in SORL1 despite substantial statistical power to detect association. While we also failed to detect association between variants in GAB2 and CSF tau levels, power to detect this association was limited. Finally, our data suggest that the minor allele of rs2986017, in CALHM1, is marginally associated with CSF Aβ42 levels. This association is consistent with previous reports that this non-synonymous coding substitution results in increased Aβ levels in vitro and provides support for an Aβ-related mechanism for modulating risk for Alzheimer’s disease.
Jeffrey Cummings, Roy Jones, David Wilkinson, Oscar Lopez, Serge Gauthier, Gunhild Waldemar, Richard Zhang, Yikang Xu, Yijun Sun, Sharon Richardson, Joan Mackell
Effect of Donepezil on Cognition in Severe Alzheimer’s Disease: A Pooled Data Analysis
Abstract: To better characterize response to donepezil in patients with severe AD, Severe Impairment Battery (SIB) data were pooled from four donepezil clinical trials (n = 904). Changes in SIB total and domain scores from baseline to week 24 were compared between placebo and donepezil treatment groups (observed case analysis). Analyses were stratified by baseline severity (Mini-Mental State Examination [MMSE] scores 1–5, 6–9, 10–12, and 13–17) to allow investigation of responses at different stages of cognitive impairment. Relationships to global and functional measures were explored. The difference between donepezil- and placebo-treated patients in least squares (LS) mean change in SIB total scores from baseline to week 24 was 6.22 (p < 0.0001, Cohen’s d, 0.53). Treatment-placebo differences were statistically significant for each baseline severity stratum, being greatest for the MMSE 6–9 stratum (LS mean difference, 7.60; p < 0.0001, Cohen’s d, 0.66). Treatment-placebo differences in LS mean change in SIB domain scores significantly favored donepezil for seven of nine domains (range, p = 0.0056 to p < 0.0001; Cohen’s d, 0.17–0.48). Change in total SIB score correlated significantly with change in measures of activities of daily living and global status. These results indicate that donepezil provides cognitive benefits in patients with severe AD, including those most markedly impaired. The treatment effect size and correlation between improvements in SIB scores and functional and global outcome measures suggest the drug–placebo differences are clinically meaningful.
Rosebud O. Roberts, James R. Cerhan, Yonas E. Geda, David S. Knopman, Ruth H. Cha, Teresa J.H. Christianson, V. Shane Pankratz, Robert J. Ivnik, Helen M. O’Connor, Ronald C. Petersen
Polyunsaturated Fatty Acids and Reduced Odds of MCI: The Mayo Clinic Study of Aging
Abstract: Mono- and polyunsaturated fatty acids (MUFA, PUFA) have been associated with a reduced risk of dementia. The association of these fatty acids with mild cognitive impairment (MCI) is not fully established. The objective of the study was to investigate the cross-sectional association of dietary fatty acids with MCI in a population-based sample. Participants aged ≥ 70 years on October 1, 2004, were evaluated using the Clinical Dementia Rating Scale (participant and informant), a neurological evaluation, and neuropsychological testing. A panel of nurses, physicians, and neuropsychologists reviewed the data for each participant in order to establish a diagnosis of MCI, normal cognition, or dementia by consensus. Participants also completed a 128-item food-frequency questionnaire. Among 1,233 non-demented subjects, 163 (13.2%) had MCI. The odds ratio (OR) of MCI decreased with increasing PUFA and MUFA intake. Compared to the lowest tertile, the OR (95% confidence interval) for the upper tertiles were 0.44 (0.29-0.66; p for trend = 0.0004) for total PUFA; 0.44 (0.30-0.67; p for trend = 0.0004) for omega-6 fatty acids; 0.62 (0.42-0.91; p for trend = 0.012) for omega-3 fatty acids; and 0.56 (0.38-0.83; p for trend = 0.01) for (MUFA+PUFA): saturated fatty acid ratio after adjustment for age, gender, number of years of education, and caloric intake. In this study, higher intake of PUFA and MUFA was associated with a reduced likelihood of MCI among elderly persons in the population-based setting.
Supplementary Data for Roberts et al. article (PDF)
Francesco Panza, Vincenza Frisardi, Davide Seripa, Bruno P. Imbimbo, Alberto Pilotto, Vincenzo Solfrizzi
Dietary Unsaturated Fatty Acids and Risk of Mild Cognitive Impairment
Abstract: An increasing body of epidemiological evidence suggested that elevated saturated fatty acids could have negative effects on age-related cognitive decline (ARCD) and mild cognitive impairment (MCI). Furthermore, a clear reduction of risk for cognitive decline has been found in population samples with elevated fish consumption, high intake of monounsaturated fatty acids, and polyunsaturated fatty acids (PUFA), particularly n-3 PUFA. In the present article, on the basis of increasing body of evidence from cross-sectional and longitudinal population-based studies, we discussed the issue of the possible impact of dietary PUFA (both n-6 and n-3) on ARCD, MCI, and Alzheimer’s disease.
John L. Woodard, Michael Seidenberg, Kristy A. Nielson, J. Carson Smith, Piero Antuono, Sally Durgerian, Leslie Guidotti, Qi Zhang, Alissa Butts, Nathan Hantke, Melissa Lancaster, Stephen M. Rao (Handling Associate Editor: Diana Woodruff-Pak)
Prediction of Cognitive Decline in Healthy Older Adults using fMRI
Abstract: Few studies have examined the extent to which structural and functional MRI, alone and in combination with genetic biomarkers, can predict future cognitive decline in asymptomatic elders. This prospective study evaluated individual and combined contributions of demographic information, genetic risk, hippocampal volume, and fMRI activation for predicting cognitive decline after an 18-month retest interval. Standardized neuropsychological testing, an fMRI scans semantic memory task (famous name discrimination), and structural MRI (sMRI) were performed on 78 healthy elders (73% female; mean age = 73 years, range = 65 to 88 years). Positive family history of dementia and presence of one or both apolipoprotein E (APOE) ε4 alleles occurred in 51.3% and 33.3% of the sample, respectively. Hippocampal volumes were traced from sMRI scans. At follow-up, all participants underwent a repeat neuropsychological examination. At 18 months, 27 participants (34.6%) declined by at least 1 SD on one of three neuropsychological measures. Using logistic regression, demographic variables (age, years of education, gender) and family history of dementia did not predict future cognitive decline. Greater fMRI activity, absence of an APOE ε4 allele, and larger hippocampal volume were associated with reduced likelihood of cognitive decline. The most effective combination of predictors involved fMRI brain activity and APOE ε4 status. Brain activity measured from task-activated fMRI, in combination with APOE ε4 status, was successful in identifying cognitively intact individuals at greatest risk for developing cognitive decline over a relatively brief time period. These results have implications for enriching prevention clinical trials designed to slow AD progression.
Jinhua Luo and Paula Grammas
Endothelin-1 is Elevated in Alzheimer’s Disease Brain Microvessels and is Neuroprotective
Abstract: The vasoactive protein endothelin-1 (ET-1) is produced by vascular endothelial cells and participates in the regulation of vascular inflammation. We have previously documented that the cerebral microvasculature is a source of inflammatory proteins and a likely contributor to the pathogenesis of Alzheimer’s disease (AD). In this study, we (a) compare expression of ET-1 in brain microvessels isolated from AD and control brains; (b) determine thrombin regulation of ET-1 synthesis and release in brain endothelial cells; and (c) assess the effects of ET-1 on neuronal viability in vitro. Western blot analysis indicates a significantly higher level of ET-1 in AD vessels compared to vessels from age-matched controls. ET-1 expression and secretion are both induced by the inflammatory and neurotoxic protein thrombin. Pretreatment of neuronal cultures with ET-1 significantly increases neuronal survival when cells are challenged with oxidative stress (H2O2) or thrombin. The protective effect of ET-1 is blocked by incubation with an inhibitor of the c-Jun kinase (JNK) cascade. These data demonstrate that in the brain microvasculature dysfunctional or stressed endothelial cells express ET-1 and that this protein promotes the survival of brain neurons exposed to injury.
Anne Rovelet-Lecrux, Didier Hannequin, Olivier Guillin, Solenn Legallic, Snejana Jurici, David Wallon, Thierry Frebourg, Dominique Campion
Frontotemporal Dementia Phenotype Associated with MAPT Gene Duplication
Abstract: Microduplications at 17q21.31 have recently been reported in children with mental retardation, autism spectrum disorders and/or dysmorphic features, as well as in a single schizophrenic patient. This rearrangement encompasses the microtubule associated protein tau (MAPT) gene, mutations of which are a major cause of frontotemporal lobar degeneration (FTLD). However, no 17q21.31 microduplication has been so far identified in this condition. We screened chromosomal rearrangements in FTLD patients using quantitative multiplex PCR of short fluorescent fragments and high resolution array CGH. We found a 439-kb microduplication at the 17q21.31 locus encompassing the MAPT, IMP5, CRHR1, and STH genes in the index case of a family in which three patients have developed a FTLD phenotype associated with marked memory impairment. None of these patients had mental retardation or dysmorphic features. Since no pathological examination was available, we are not certain that this case corresponds to a FTLD with neuronal and glial tau inclusions (FTLD-tau), and we cannot exclude that any other gene included in the rearrangement might be responsible for the neurodegenerative process. However, the clinical phenotype of the three patients is functionally consistent with the regional pattern of lesions previously reported in mice overexpressing human tau.
Joseph F. Quinn, Christopher J Harris, , Katherine E. Cobb, Christopher Domes, Martina Ralle, George Brewer, Teri L. Wadsworth (Handling Associate Editor: Ashley Bush)
A Copper-Lowering Strategy Attenuates Amyloid Pathology in a Transgenic Mouse Model of Alzheimer’s Disease
Abstract: There is increasing evidence for the crucial role of metals in the pathology of Alzheimer’s disease. Both the aggregation and neurotoxicity of amyloid-β are dependent on the presence of copper. This study investigated the ability of the copper-complexing drug tetrathiomolybdate to reduce amyloid-β pathology and spatial memory impairment in both a prevention and a treatment paradigm in the Tg2576 mouse model of Alzheimer’s disease. Tetrathiomolybdate treatment lowered brain copper and reduced amyloid-β levels in the prevention paradigm, but not in the treatment paradigm. Our data suggests that controlled lowering of systemic copper may achieve anti-amyloid effects if initiated early in the disease process.
Anna Chiarini, James Whitfield, Clara Bonafini, Balu Chakravarthy, Ubaldo Armato, Ilaria Dal Prà
Amyloid-β25-35, an Amyloid-β1-42 Surrogate, and Proinflammatory Cytokines Stimulate VEGF-A Secretion by Cultured, Early Passage, Normoxic Adult Human Cerebral Astrocytes
Abstract: Cerebrovascular angiopathy affects late-onset Alzheimer’s disease (LOAD) brains by possibly increasing vascular endothelial growth factor (VEGF-A) expression, thereby stimulating endothelial cell proliferation and migration. Indeed, VEGF-A gene upregulation with increased VEGF-A protein content of reactive astrocytes and microglia, occurs in LOAD brains, and neovascularization was observed one week after injecting amyloid-β (Aβ)1-42 into rat hippocampus. We have now found, within cultured 'normoxic' normal adult human astrocytes (NAHAs), that fibrillar Aβ25-35 (an active Aβ1-42 fragment) or a cytokine mixture (the (CM)-trio (interleukin [IL]-1β + interferon [IFN]-γ + tumor necrosis factor [TNF]-α), or pair (IFN-γ + TNF-α) like those produced in LOAD brains) stimulates the nuclear translocation of stabilized hypoxia-inducible factor (HIF)-1α protein and its binding to VEGF-A hypoxia-response elements; the mRNA synthesis for three VEGF-A splice variants (121, 165, 189); and the secretion mainly of VEGF-A165. The CM-trio was the most powerful stimulus, IFN-γ + TNF-α was less potent, and other cytokine pairs or single cytokines or Aβ35-25 were ineffective. While Aβ25-35 left unchanged HIF-1β protein levels, the CM-trio increased both HIF-1α and HIF-1β protein levels, thereby giving an earlier and stronger stimulus to VEGF-A secretion by NAHAs. Thus, increased VEGF-A secretion from astrocytes stimulated by Aβ1-42 and by microglia-released cytokines might restore angiogenesis and Aβ1-42 vascular clearance.
Marina Saresella, Elena Calabrese, Ivana Marventano, Federica Piancone, Andrea Gatti, Maria Gaetana Calvo, Raffaello Nemni, Mario Clerici (Handling Associate Editor: Daniela Galimberti)
PD1 Negative and PD1 Positive CD4+ T Regulatory Cells in Mild Cognitive Impairment and Alzheimer’s Disease
Abstract: Regulatory T lymphocytes (Treg) play a fundamental importance in modulating the relative balance between inflammation and immune tolerance, and alterations of these cells are observed in inflammatory diseases. To better characterize the neuroinflammatory processes suggested to be associated with Alzheimer’s disease (AD) and to clarify the possible role of Treg cells in this process, we extensively analyzed these cells (CD4+CD25highFoxp3+) in patients with either severe AD (n = 25) or mild cognitive impairment (MCI) (n = 25), comparing the results with those of two groups of healthy controls (HC) (n = 55). Because the intra- or extracellular expression of programmed death receptor 1 (PD1) identifies functionally diverse subsets of Treg we also analyzed such subpopulations. Results showed that, whereas both Treg and PD1pos Treg are increased in MCI and AD patients compared to HC, PD1neg Treg, the subpopulation of Treg cells endowed with the strongest suppressive ability, are significantly augmented in MCI patients alone. In these patients amyloid-β-stimulated-T cells proliferation was reduced and Treg-mediated suppression was more efficient compared to both AD and HC. The observation that PD1neg Treg, cells are increased in MCI patients reinforces the inflammatory origin of AD and supports a possible beneficial role of these cells in MCI that is lost in patients with full-blown AD.
Bong Geom Jang*, Sang-MoonYun*, Kyungsook Ahn, Ju Hee Song, Sangmee A. Jo, Young-Yul Kim, Doh Kwan Kim, Moon Ho Park, Changsu Han, Young Ho Koh (Handling Associate Editor: D. Allan Butterfield) *These authors contributed equally to this work.
Plasma Carbonic Anhydrase II protein is Elevated in Alzheimer’s Disease
Abstract: Carbonic anhydrase (CA) plays a critical role in pH regulation, long-term synaptic transformation, and is associated with mental retardation, Alzheimer’s disease (AD), and Down syndrome. There is accumulating evidence that CAII is increased in AD brain. The present study focused on the determination of CAII protein level in blood plasma samples using immunoblot and ELISA methods. We compared plasma from 91 AD patients (average age 74.8 y), 83 persons with amnestic mild cognitive impairment (MCI) (average age 73.5 y), and 113 cognitively normal controls (average age 70.8 y). The plasma level of CAII was significantly increased in AD patients, as compared to control groups. CAII levels were higher in males than females. There was an age-dependent increase of CAII. These results provide further evidence that changes in CAII level may play a role in the pathogenesis of AD.
Yawu Liu, Teemu Paajanen, Eric Westman, Lars-Olof Wahlund, Andrew Simmons, Catherine Tunnard, Tomasz Sobow, Petroula Proitsi, John Powell, Patrizia Mecocci, Magda Tsolaki, Bruno Vellas, Sebastian Muehlboeck, Alan Evans, Christian Spenger, Simon Lovestone, Hilkka Soininen for the AddNeuroMed Consortium
Effect of APOE ε4 Allele on Cortical Thicknesses and Volumes: The AddNeuroMed Study
Abstract: The apolipoprotein E (APOE) ε4 allele is a risk factor for Alzheimer’s disease (AD), but its effect on brain volumes is controversial. We explored the effect of the ε4 allele on regional cortical thickness and volume measurements using an automated pipeline in 111 subjects with mild cognitive impairment (MCI), 115 AD patients, and 107 age-matched healthy controls. The clinical data were used as covariates in the thickness and volume comparisons. The ε4 carriers had significantly smaller volume than non-carriers in caudate (p = 0.028) in controls; in amygdala and caudate in the MCI group (p ≤ 0.049); and in hippocampus and amygdala in the AD group (p ≤ 0.001). In the female subjects, the ε4 carriers had significantly thinner cortical thickness or volume than non-carriers in medial orbitofrontal gyrus and caudate in controls (p ≤ 0.014); in amygdala in MCI subjects (p = 0.047) and in hippocampus and amygdala in AD patients (p ≤ 0.024). However, in the male subjects, there were significant differences in cortical thickness and volume between ε4 carriers and non-carriers in several structures in the MCI group, but no differences in the controls and AD patients. Compared to the non-carriers, the homozygous ε4 carriers showed significant volume loss in hippocampus, deep nuclei, and caudal anterior cingulate cortex in MCI. In the AD group, the homozygous ε4 carriers had significant volume loss in hippocampus and amygdala. We conclude that the APOE ε4 allele modulates regional cortical thickness and volume in relation to diagnostic group and gender. The ε4 allele has a dose-dependent and regionally specific effect on brain structures.
Suzanne M. de la Monte, Ming Tong, VanAhn Nguyen, Mashiko Setshedi, Lisa Longato, Jack R. Wands
Ceramide-Mediated Insulin Resistance and Impairment of Cognitive-Motor Functions
Abstract: Obesity, type 2 diabetes mellitus (T2DM), and non-alcoholic steatohepatitis (NASH) are associated with cognitive impairment, brain insulin resistance, and neurodegeneration. Recent studies linked these effects to increased pro-ceramide gene expression in liver and increased ceramide levels in serum. Since ceramides are neurotoxic and cause insulin resistance, we directly examined the role of ceramides as mediators of impaired signaling and central nervous system function using an in vivo model. Long Evans rat pups were administered C2Cer:N-acetylsphinganine or its inactive dihydroceramide analog (C2DCer) by i.p. injection. Rats were subjected to rotarod and Morris water maze tests of motor and cognitive function, and livers and brains were examined for histopathology and integrity of insulin/IGF signaling. C2Cer treatment caused hyperglycemia, hyperlipidemia, and mild steatohepatitis, reduced brain lipid content, and increased ceramide levels in liver, brain, and serum. Quantitative RT-PCR analysis revealed significant alterations in expression of several genes needed for insulin and IGF-I signaling, and multiplex ELISAs demonstrated inhibition of signaling through the insulin or IGF-1 receptors, IRS-1, and Akt in both liver and brain. Ultimately, the toxic ceramides generated in peripheral sources such as liver or adipose tissue caused sustained impairments in neuro-cognitive function and insulin/IGF signaling needed for neuronal survival, plasticity, and myelin maintenance in the brain. These findings support our hypothesis that a liver/peripheral tissue-brain axis of neurodegeneration, effectuated by increased toxic lipid/ceramide production and transport across the blood-brain barrier, could mediate cognitive impairment in T2DM and NASH.
Clive Bate and Alun Williams (Handling Associate Editor: James Bamburg)
Amyloid-β1-40 Inhibits Amyloid-β1-42 Induced Activation of Cytoplasmic Phospholipase A2 and Synapse Degeneration
Abstract: The pathogenesis of Alzheimer’s disease (AD) is associated with the accumulation of amyloid-β (Aβ) peptides and the loss of synapses. The addition of Aβ1-42 reduced the amount of synaptophysin in cultured cortical neurons in a model of AD-induced synapse degeneration. Aβ1-42 also reduced the uptake of the fluorescent dye FM1-43 into synaptic recycling vesicles, a measure of synaptic function. We report that pre-mixing Aβ1-40 with Aβ1-42 significantly reduced the effects of Aβ1-42 on synapses; it increased both synaptic vesicle recycling and synaptophysin content. These results are consistent with reports that Aβ1-40 forms oligomers with Aβ1-42 and that these are less toxic than Aβ1-42 alone. In contrast, the addition of Aβ1-40 did not affect the synapse degeneration induced by the prion-derived peptide PrP82-146. The addition of Aβ1-40 reduced Aβ1-42 induced activation of cytoplasmic phospholipase A2 (cPLA2) within synapses consistent with the hypothesis that Aβ1-42 induced synapse degeneration is mediated by aberrant activation of synaptic cPLA2. Such observations raise the possibility that the amount of Aβ1-40 produced within the brain is critical in determining the synapse damaging effects of Aβ1-42 and possibly the cognitive loss seen during the early stages of AD.
Shizuo Hatashita, Hidetomo Yamasaki
Clinically Different Stages of Alzheimer’s Disease Associated by Amyloid Deposition with [11C]-PIB PET Imaging
Abstract: We investigated whether [11C]-PIB PET detects underlying amyloid deposition at clinically different stages of Alzheimer’s disease (AD) and preclinical dementia. The Japanese cohort of 214 subjects underwent cognitive testing and 60-min dynamic [11C]-PIB PET. [11C]-PIB data were acquired from 35-60 min after injection. Regions of interest were defined on co-registered MRI. Distribution volume ratios (DVR) of PIB retention were determined using Logan graphical analysis. All 56 patients with AD showed a robust increase in PIB retention in cortical areas (typical PIB AD-pattern). Mean DVR value in 11 patients with moderate AD (CDR: 2.1 ± 0.4) showed significantly higher PIB retention (2.38 ± 0.42, p < 0.01) than amyloid-negative healthy control (HC) subjects. The DVR values in 23 patients with very mild AD (CDR: 0.5) and 22 patients with mild AD (CDR: 1.0) were 2.32 ± 0.45 and 2.34 ± 0.42, respectively, similar to moderate AD. In contrast, 28 (48%) of the 58 mild cognitive impairment (MCI) patients (MMSE: 27.3 ± 1.7) showed a typical AD-like pattern with a DVR value of 2.07 ± 0.34. Further, 17 (18%) of 91 HC subjects had a typical AD-like pattern with a DVR value of 2.06 ± 0.28. They did not significantly differ from very mild AD. The prevalence of AD among the 53 amyloid positive patients aged 75 years or older increased greatly to 74% whereas that of amyloid positive HC decreased by only 9% and amyloid positive MCI by 17%. Prodromal AD and AD dementia is identified, based on cognitive function and amyloid deposition by PIB PET imaging. Further, the cortical amyloid deposition could be detected at preclinical stage of AD.
Erik Portelius, Bianca Van Broeck, Ulf Andreasson, Mikael K. Gustavsson, Marc Mercken, Henrik Zetterberg, Herman Borghys, Kaj Blennow
Acute Effect on the Aβ Isoform Pattern in CSF in Response to γ-Secretase Modulator and Inhibitor Treatment in Dogs
Abstract: Alzheimer’s disease (AD) is associated with deposition of amyloid-β (Aβ) in the brain, which is reflected by low concentration of the Aβ1-42 peptide in the cerebrospinal fluid (CSF). The γ-secretase inhibitor LY450139 (semagacestat) lowers plasma Aβ1-40 and Aβ1-42 in a dose-dependent manner but has no clear effect on the CSF level of these isoforms. Less is known about the potent γ-secretase modulator E2012. Using targeted proteomics techniques, we recently identified several shorter Aβ isoforms in CSF, such as Aβ1-16, which is produced by a novel pathway. In a Phase II clinical trial on AD patients, Aβ1-14, Aβ1-15 and Aβ1-16 increased several-fold during γ-secretase inhibitor treatment. In the present study, 9 dogs were treated with a single dose of the γ-secretase modulator E2012, the γ-secretase inhibitor LY450139, or vehicle with a dosing interval of 1 week. The CSF Aβ isoform pattern was analyzed by immunoprecipitation combined with MALDI-TOF mass spectrometry. We show here that Aβ1-15 and Aβ1-16 increase while Aβ1-34 decreases in response to treatment with the γ-secretase inhibitor LY450139, which is in agreement with previous studies. The isoform Aβ1-37 was significantly increased in a dose-dependent manner in response to treatment with E2012, while Aβ1-39, Aβ1-40 and Aβ1-42 decreased. The data presented suggests that the γ-secretase modulator E-2012 alters the cleavage site preference of γ-secretase. The increase in Aβ1-37 may inhibit Aβ1-42 oligomerization and toxicity.
Franck Hansmannel, Adeline Sillaire, M. Ilyas Kamboh, Corinne Lendon, Florence Pasquier, Didier Hannequin, Geoffroy Laumet, Anais Mounier, Anne-Marie Ayral, Steven T. DeKosky, Jean-Jacques Hauw, Claudine Berr, David Mann, Philippe Amouyel, Dominique Campion, Jean-Charles Lambert
Is the Urea Cycle Involved in Alzheimer’s Disease?
Abstract: Since previous observations indicated that the urea cycle may have a role in the Alzheimer’s disease (AD) process, we set out to quantify the expression of each gene involved in the urea cycle in control and AD brains and establish whether these genes could be genetic determinants of AD. We first confirmed that all the urea cycle enzyme genes are expressed in the AD brain. The expression of arginase 2 was greater in the AD brain than in the control brain. The presence of the rare arginase 2 allele rs742869 was associated with an increase in the risk of AD in men and with an earlier age-at-onset for both genders. None of the other genes in the pathway appeared to be differentially expressed in the AD brain or act as genetic determinants of the disease.
Supplementary Data for Hansmannel et al. article (PDF)
Book Review: Neurological Disorders in Famous Artists, Part 3,
Volume Editors J. Bogousslavsky, M.G. Hennerici, H. Bazner, C. Bassetti, Karger Publishers, Frontiers in Neurology and Neuroscience, Volume 27, 2010. Reviewed by Robert P. Friedland
Meeting Report from the Alzheimer Research Forum
Alzheimer’s Prevention Initiative